1. Technical Field
The present invention relates to an image reading apparatus and a semiconductor device.
2. Related Art
An image reading apparatus (scanner) using a contact image sensor, and a copying machine, a combined printer, or the like to which a printing function is added have been developed. As the contact image sensor used in the image reading apparatus, a configuration of using a photodiode which is provided on a semiconductor substrate is used.
For example, JP-A-5-207375 discloses a solid-state imaging element (imaging sensor) including a pixel (basic cell). The pixel includes a photodiode, a feedback capacitance element which accumulates photoelectric charges generated in the photodiode, an amplification circuit which uses an n-type MOS transistor, and a reset switching element for disconnecting an input terminal and an output terminal of the amplification circuit (source and drain of the n-type MOS transistor).
JP-A-5-207375 discloses that a capacitance value of the feedback capacitance element is decreased, and thus it is possible to improve sensitivity of a pixel. However, in the pixel (basic cell) disclosed in JP-A-5-207375, if the capacitance value of the feedback capacitance element is set to be small, a dynamic range of an output signal from the pixel (basic cell) is narrowed due to charge injection. Thus, in the image reading apparatus (scanner) of the related art, it is difficult to improve sensitivity in reading an image.